In recent years, storage systems which include a host device, a tape library device, and a virtual tape device have been used. In such a system, the virtual tape device is provided between the host device and the tape library device and stores therein, as a virtual tape volume (logical volume), data transmitted and received between the host device and the tape library device. As described above, the virtual tape device places data as a logical volume on a random access medium (for example, a tape volume cache; TVC) such as a magnetic disk device or the like, and thus, virtually performs tape operations on the magnetic disk medium. This allows the virtual tape device to omit mechanical operations, such as tape mount, load/unload, and the like, thus realizing high-speed operations.
In the above-described storage system, as the expiration date of support for the virtual tape device approaches, a system user (customer) purchases a new virtual tape device and performs a data migration operation to migrate data from the old virtual tape device to the new virtual tape device.
As for existing data migration, for example, an old virtual tape device and a new virtual tape device are provided together for a host device and desired data is moved (copied) from the old virtual tape device to the new virtual tape device via the host device, thus performing data migration (see, for example, FIG. 10).
As another example, existing data migration is performed, by using an export/import function, which is one of functions of the virtual tape device. That is, desired data which exists in the old virtual tape device is written on a tape which is a physical volume by an export function of the old virtual tape device. Thereafter, the tape on which the desired data is written is moved to a tape library which belongs to the new virtual tape device and the desired data is read from the tape which has been moved into the new virtual tape device by an import function of the new virtual tape device, thus performing data migration.
Related techniques are disclosed, for example, in Japanese Laid-open Patent Publication No. 2007-265403 and International Publication Pamphlet No. WO2009/040954.
However, when desired data is copied from the old virtual tape device to the new virtual tape device via the host device, data stored in the old virtual tape device is read and is temporarily stored in the host device, and then, the stored data is written to the new virtual tape device. Therefore, a problem arises in which it takes a long time (from several days to several weeks) to complete moving of all of the desired data and enable normal operations of the storage system.
When data migration is performed using the export/import function, data writing to a tape is performed in the old virtual tape device and data reading from a tape is performed in the new virtual tape device. Therefore, a problem arises in which it takes a long time (from several days to several weeks) to complete moving of all of the desired data and enable normal operations of the storage system.